[FEA] store node, edge file_id and dataset_id

[lmeyerov]

Is your feature request related to a problem? Please describe.

In python flows like g.plot(), it would be quite handy to be able to get the node_file_id, edge_file_id, and dataset_id

This came up in some recent testing work. with the new remote endpoints, presumably, this will become even more natural.

Describe the solution you'd like

1. New Plottable fields _node_file_id, _edge_field_id, _dataset_id, _url

2. plot(inplace=True) => fields update to original Plottable; default on

g.plot(inplace=True)
...
print(g._node_file_id, g._edge_file_id, g._dataset_id)

Convenient default for typical notebook plotting use

3. plot(return_plottable=true) => return Plottable, with new fields; default off

g2 = g1.plot(return_plottable=True)
print(g._url, g._node_file_id, g._edge_file_id, g._dataset_id)

Convenient flag for typical app dev flows